Tensioner

ABSTRACT

A tensioner, for clamping cables, flexible pipes or bars and moving them forwards in a controlled manner, includes at least two conveyors, each intended to displace one or more clamping members. The conveyors each attached to a main frame element. A selective number of the conveyors can be combined using standard connection elements.

BACKGROUND OF THE INVENTION

The invention relates to a tensioner, for clamping cables, flexiblepipes or bars and moving them forwards in a controlled manner,comprising at least two conveyor means, each intended to displace one ormore clamping members, the she of which is adapted to the external shapeof the cables, flexible pipes or bars, and the conveyor means each beingattached to a main frame element, all this in such a manner that theclamping members can be displaced while clamped around the cables,flexible pipes or bars.

Tensioners are used, inter alia, when laying cables and flexible pipesfrom a ship, for example on the sea bed. The cables, the flexible pipesor the bars are guided from the ship towards the sea bed using thetensioner, via the so-called S- or J-method. If the S-method is used,the cable or the flexible pipe leaves the ship essentially in thehorizontal direction, and the cable or the flexible pipe will beconnected to the part which has already been positioned on the sea bed(ground) via an S-bend. If the J-method is used, the cable or theflexible pipe leaves the ship essentially in the vertical direction andis connected to the part which has already been laid on the ground via aJ-shaped bend.

The role of the tensioner is twofold. Firstly, the tensioner has to beable to clamp the cable or the flexible pipe fixedly, in order toprevent it leaving the ship at an uncontrolled speed as a result of theweight of the section which is transferred, overboard. The weight whichthe tensioner has to stop in this way can rise to a very high level. Thetensioner therefore has to be able to exert a high clamping force on thecable or the flexible pipe. The second role of the tensioner is to movethe cables and the flexible pipes forwards. The maximum speed at whichthis takes place is dependent, inter alia, on the condition of theground at that location. Moreover, the cable or the flexible pipe inmost cases still has to be assembled on the deck of the ship duringlaying. The speed at which the assembled pan is moved overboard istherefore dependent on the time which is required for assembling thecable or the flexible pipe itself.

In order to be able to satisfy the demands placed on the tensioners,generally at least two endless conveyors are incorporated in thetensioners according to the prior art. By moving the conveyors towardsone another with a considerable force, a high clamping force can beexerted on the cable or flexible pipe positioned between them. By thendriving the conveyors, the cable or the flexible pipe can be advancedwithout losing the clamping force. Since the cables and the flexiblepipes have an essentially round cross-section, the conveyors in atensioner with two conveyors therein are positioned at an angle of 180°.In a tensioner with three conveyors, they form an angle of 120° withrespect to one another, and in the case of four conveyors their mutualangle is in each case 90°.

A significant drawback of the tensioners according to the prior art isthat the design of a tensioner and the number of conveyors which arefitted therein depends on the typo of cable or flexible pipe for whichthe tensioner is designed For example, a flexible pipe with, forexample, a large diameter and a relatively thin wall may be pressed intoan elliptical shape by two conveyors. For this reason, the tensioner forflexible pipes of this nature is generally equipped with three or fourconveyors. This means tat the operators of the ships for laying cablesand flexible pipes have to purchase a separate tensioner for each typeof cable or flexible pipe, a fact which entails relatively highinvestment costs.

Another significant drawback of the tensioners according to the priorart is, furthermore, that there is generally only one tensioner on boarda ship, owing to lack of space. It is therefore impossible to changefrom one type of tensioner to another type of tensioner while at sea.

A third drawback of the tensioners according to the prior art is thatthe tensioners are relatively bulky. Owing to the size and weight of thetensioners according to the prior art, they are extremely expensive totransport.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a tensioner which doesnot exhibit the drawbacks of the tensioners according to the prior art.

In order to achieve his object, the tensioner according to the presentinvention is provided with conveyor means with clamping members, inwhich the conveyor means with the clamping members are of modulardesign, such that various tensioner designs can be constructed with theaid of a number of conveyor means and a number of main frame elements.

The advantage of a tensioner of modular design is firstly the fact thatvarious tensioners can be put together with the aid of a limited numberof (at least two) identical conveyor means. The availability of thetensioner which is to be of modular construction means that it is notnecessary to purchase a new type of tensioner for each new type of cableor flexible pipe. Instead of a large number of different tensioners, auser only needs to purchase a limited number of these conveyor means.Moreover, the tensioners which are to be of modular construction are ofrelatively low weight and can be put together in a compact manner.

It is attempted to make the conveyor means with the clamping members ofmodular design in such a manner that they fit in an ISO container.

By adapting the dimensions of the conveyor means to the size of ISOcontainers, the conveyor means can be transported in a container orinstead of a container. Transporting a tension according to the priorart always requires special precautionary measures and is thereforerelatively expensive. By adapting the dimensions of the conveyor meansto the dimensions of ISO containers, transporting the tensioner modulesaccording to the present invention does not require any specialprecautionary measures. The transport costs for a modular tensioner willtherefore be much lower than the transport costs for a bulky tensioneraccording to the prior art.

It is advantageous if the conveyor means comprise attachment eyelets forattaching the conveyor means to a main frame element.

The advantage of this measure is that a tensioner according to thepresent invention can be put together or altered easily and in arelatively short time.

The tensioner according to the present invention is improved stillfurther if the conveyor means comprise a base frame and a conveyor whichis arranged displaceably thereon, the conveyor being attached to thesaid base frame with the aid of at least one hydraulic cylinder and atleast a first and a second pivot arm such that it can move essentiallyparallel with respect to the said base frame.

Moreover, in this case it is advantageous if the hydraulic cylinder andthe pivot arms are all attached both to the base frame and to theconveyor, the attachment position of the hydraulic cylinder on the baseframe corresponding to the attachment position of the first pivot armthereon, and the attachment position of the cylinder on the conveyorcorresponding to the attachment position of the second pivot armthereon.

The advantage of a design of this nature is the only the hydrauliccylinder has to be actuated in order to displace the conveyor withrespect to the base frame. In this design, the conveyor is kept parallelalong the base frame by means of the pivot arms.

In an advantageous embodiment of the present invention, the conveyormeans comprise a conveyor which is provided with a drive chain of doubledesign.

By employing a double chain, the conveyor will be less inclined to startto tilt, since the support provided by the belt is made wider. In amanner of speaking, the “wheel base” of the belt becomes wider as aresult of a double chain being used. This measure improves the stabilityof the tensioner according to the present invention considerably bycomparison with tensioners according to the prior art.

The present invention relates not only to a tensioner but also to aconveyor means of modular design which is intended for the tensioneraccording to the present invention. It is advantageous here for at leasttwo conveyor means according to the present invention to be connected toone another by means of main frame elements, in which case preferably alimited number of variants of the said main frame elements aresufficient for constructing a tensioner having 2, 3, 4 or more conveyormeans, as desired. This has the advantage that a tensioner which issuitable for any type of cable or flexible pipe can be constructed usinga limited number of means together with a limited number of frameelements. Furthermore, this offers the possibility of very compactdesign.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction and use of the present invention will be explained withreference to the following drawings, in which;

FIG. 1 diagrammatically depicts how a cable or a flexible pipe is movedoverboard via the S-method;

FIG. 2 diagrammatically depicts how a cable or a flexible pipe is movedoverboard via the J-method;

FIG. 3 is a side view of the conveyor means according to the presentinvention;

FIG. 4 is a cross-section on line IV—IV of the conveyor means inaccordance with FIG. 3;

FIG. 5 is a cross-section of a tensioner with three conveyor meansaccording to the present invention therein;

FIG. 6 is a cross-section of a tensioner with two or four conveyor meansaccording to the present invention therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 diagrammatically depicts the case in which a tensioner 2 which ispositioned on a ship 1 is used to lay a cable or a flexible pipe 4 onthe bed 5 of, for example, the sea via the so-called S-method. It can beseen in FIG. 1 that the cable or the flexible pipe 4 leaves the ship 1essentially in the horizontal direction, That part of the cable orflexible pipe 4 which is clamped fixedly by means of the tensioner 2 isconnected via an S-bend to the part which has already been laid on thebed 5.

FIG. 2 diagrammatically depicts the case in which a cable or a flexiblepipe 4 is laid on the bed 5 of, for example, the sea from a ship 1, withthe aid of a tensioner 2, via the so-called J-method. It can be seen inthe figure that the cable or flexible pipe 4 leaves the ship 1essentially in the vertical direction. That part of the cable or theflexible pipe 4 which is clamped fixedly by means of the tensioner 2 isconnected in a J-shaped bend to the part which has already been placedon the bed 5.

It can be seen from FIGS. 1 and 2 that the tensioner 2 has twofunctions. Firstly, the tensioner 2 has to prevent the cable or theflexible pipe 4 from leaving the ship 1 of its own accord as a result ofits own weight. For this reason, the tensioner 2 has to be able to clampthe cable or the flexible pipe 4 fixedly. Secondly, the tensioner 2 hasto be able to move the cable or flexible pipe 4 overboard without losingthis clamping force. The tensioner 2 is therefore provided with at leasttwo conveyor means 3, comprising conveyors. The conveyors can be movedtowards one another in order to clamp a cable or flexible pipe 4fixedly. By moreover driving the conveyors, the cable or flexible pipe 4can leave the ship 1 at a controlled speed.

FIG. 3 shows the conveyor means according to the present invention, Theconveyor means 3 comprise a base frame 31 and a conveyor 39 which isarranged movably with respect to this base frame 31. The conveyor 39 isattached, for example, to the base frame 31 with the aid of at least onehydraulic cylinder 32 and two pivot arms 33. The hydraulic cylinder 32and the pivot arms 33 are preferably attached to the base frame 31 viaattachment eyelets 34. For its part, the conveyor 39 comprises, interalia, clamping members 35 which can be pushed onto a cable or flexiblepipe 4 which is to be displaced. The clamping members 35 are positionedon a chain 36. This chain 36 is preferably of double design, in order tobe able to support the clamping members 35 over their width (of FIG. 4).The chain 36 of the conveyor is advanced, for example, with the aid of atoothed wheel 37. Moreover, the base frame 31 is provided withattachment eyelets 38, by means of which the conveyor means 3 can beconnected in a simple manner to, for example, a main frame.

FIG. 4 shows a cross-section of the conveyor means 3 on line IV—IV, inaccordance with FIG. 3. The double chain 36 ensures that the clampingmembers 35 cannot tilt with respect to the base frame 31, not even ifthese members 35 are subjected to relatively high compressive forces. Itis advantageous if the clamping members 35 have an essentially annularor V-shaped recess 40 on their outwardly directed surface. As a resultthe overall circumference which the clamping members 35 of conveyors 39placed in a tensioner (cf. FIGS. 5 and 6) delimit will also be annular.

FIG. 5 shows a tensioner which is composed of three conveyor means 3according to the present invention. The modules 3 are attached to oneanother with the aid of main frame elements 50. It can be seen in thefigure that the main frame elements 50 are connected to the conveyormeans 3 via the attachment eyelets 38.

FIG. 6 shows the situation where a cable or a flexible pipe 4 is soundedby two or four (shown in dashed lines) conveyor means 3 according to theinvention.

It can be seen from FIGS. 5 and 6 that it is possible, as desired, toassemble two, three, four or, if desired, even more conveyor means 3according to the present invention to form one tensioner. The number ofconveyor means 3 to be used will depend on, inter alia, the thickness,the stiffness and the weight of the cable or flexible pipe to bedisplaced. The advantage of this is that it is not necessary to build aspecial tensioner for each type of cable or flexible pipe. Variousdifferent tensioners can be constructed using a limited number ofconveyor means 3 according to the present invention and a number ofstandard main frame elements 50.

What is claimed is:
 1. A tensioner assembly comprising: plural separateconveyors and plural connection elements that connect said conveyorstogether in plural different connection arrangements wherein a tensionerformed by the tensioner assembly includes a selectable number of saidconveyors; each of said conveyors comprising plural clamping membersthat are arranged to engage a body to be conveyed, an endless chaincarrying said plural clamping members, a base frame that adjustablycarries said endless chain, and attachment points in said base frame;and each of said connection elements comprising connectors at endsthereof for connection to respective ones of said attachment points tocreate the plural different connection arrangements.
 2. The tensionerassembly of claim 1, wherein said connection elements are rods with acommon length.
 3. The tensioner assembly of claim 1, wherein for each ofsaid conveyors a position of said endless chain relative to a body to beconveyed is adjustable independent of a position of another said endlesschain.
 4. The tensioner assembly of claim 3, wherein each of saidconveyors comprises hydraulic cylinders attached to said base frame thatadjust a distance of said endless chain from said base frame.
 5. Thetensioner assembly of claim 1, wherein each said endless chain is adouble chain.
 6. The tensioner assembly of claim 1, including four ofsaid conveyors.
 7. Then tensioner assembly of claim 6, wherein saidattachment points are eyelets, each of said conveyors compriseshydraulic cylinders attached to said base frame that adjust a distanceof said endless chain from said base frame, and each said endless chainis a double chain.
 8. The tensioner assembly of claim 1, wherein allfour of said conveyors are connected by said connection elements to forma tensioner with four conveyors at 90° intervals.